Performance characteristics of Ti-Ag contact N/P and P/N silicon solar cells
Ti-Ag contact N-P and P-N single crystal Si solar cells electrical and mechanical performance characteristics
Schmidt, L. W.↗
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Inhibition of methanol cracking of Ti-6Al-4V foil - Effect of pretreatments with aqueous solutions of electrolytes
Methanol stress corrosion cracking of Ti-Al-V foil inhibited by pretreatment in aqueous solutions of electrolytes, discussing colloidal character of microcrystallites
Fugassi, P.↗
Extreme-ultraviolet spectra of Sc XIV, Ti XV, and V XVI
Extreme UV spectra of Sc XIV, Ti XV and V XVI, identifying and classifying lines in 18-25 A range
Cohen, L.↗
Effect of stress on microsegregation of hydrogen at elevated temperatures in titanium and Ti-8Al-1Mo-1V
Stress effect on hydrogen distribution at high temperatures in titanium and Ti-Al-Mo-V alloy
Mackay, T. L.↗
The influence of temperature on fatigue-crack growth in a mill annealed Ti-6Al-4V alloy
To understand the influence temperature on the rate of fatigue crack growth in high strength metal alloys, constant load amplitude, fatigue crack growth experiments were carried out using a 1/4-inch-thick (6.35 mm) mill annealed Ti-6Al-4V alloy plate as a model material. The rates of fatigue crack growth were determined as a function of temperature, ranging from room temperature to about 290 C (or, about 550 F/563K) and as a function of the crack tip stress intensity factor in a dehumidified high purity argon environment. Limited correlative experiments indicate that dehumidified oxygen and hydrogen have no effect on the rate of fatigue crack growth in this alloy, while distilled water increased the rate of crack growth slightly in the range tested. Companion fractographic examinations suggest that the mechanisms for fatigue crack growth in the various environments are essentially the same.
Wei, R. P.↗
Fractographic observations of Ti-6Al-4V alloy fatigued in vacuum.
These observations were made as part of a study of the influence of temperature and chemical environment on fatigue-crack growth. The results obtained, along with additional fractographic results in other environments, suggest that the mechanism for fatigue-crack growth in the Ti-6Al-4V alloy is basically similar (striations are observed) for a wide range of environments. In addition to ?vacuum,' these environments include distilled water, ?dry' and ?wet' air, ?dry' hydrogen, and ?dry' and ?wet' argon.
Ritter, D. L.↗
Hydrogen-enhanced fatigue crack growth in Ti-6Al-4V ELI weldments.
The effects of a hydrogen environment on the fatigue crack growth rates in Ti-6Al-4V ELI (STA) and weld material were determined in the temperature range of ambient to -200 F. The hydrogen environment resulted in an acceleration of the crack growth rate and a change in the fracture mode for both materials in the temperature range of ambient to -100 F. At -200 F, there was no significant difference between the crack growth rates obtained in helium and hydrogen gas. The degree of hydrogen-enhanced crack growth was found to be dependent on the crack tip stress-intensity range, temperature, and microstructure of the material. The data are consistent with an embrittlement mechanism involving hydrogen diffusing ahead of the crack front.
Pittinato, G. F.↗
SCC of Ti-6Al-4V foil by methanol - Effect of treatments with 2,4-pentanedione and its metal complexes.
The susceptibility of Ti-6Al-4V foil to stress corrosion cracking (SCC) by methanol can be decreased by treatment of the foil with 2,4-pentanedione prior to its immersion in the corroding media. It is assumed that such treatments remove from the protective film formed on the foil by exposure to the atmosphere, certain metal ions whose oxides are more readily penetrated by the ions, Na + and Cl- or Fe(3+) and Cl-, present in the corroding media.
Haney, E. G.↗
The influence of temperature on fatigue crack growth in a mill annealed Ti-6Al-4V alloy.
To study the influence of temperature on the rate of fatigue crack growth in high strength metal alloys, constant load amplitude fatigue crack growth experiments were carried out using a .25-in.-thick mill annealed Ti-6Al-4V alloy plate. The rates of fatigue crack growth were determined as a function of temperature, ranging from room temperature to about 290 C, and as a function of the crack tip stress intensity factor in a dehumidified high purity argon environment. Limited correlative experiments were carried out in distilled water, dehumidified oxygen and hydrogen, and in vacuum. The results indicate that the rate of fatigue crack growth is essentially independent of test temperature in this alloy, and is affected by residual moisture in very small concentrations. Companion fractographic examinations suggest that the mechanims for fatigue crack growth in the various environments are essentially the same.
Wei, R. P.↗
Gaseous hydrogen-induced cracking of Ti-5Al-2.5Sn.
Study of the kinetics of hydrogen-induced cracking in the Ti-5Al-2.5Sn titanium alloy, which has a structure of acicular alpha platelets in a beta matrix. The crack-growth rate at low stress-intensity levels was found to be exponentially dependent on stress intensity but essentially independent of temperature. The crack-growth rate at intermediate stress-intensity levels was found to be independent of stress intensity but dependent on temperature in such a way that crack-growth rate was controlled by a thermally activated mechanism having an activation energy of 5500 cal/mole and varied as the square root of the hydrogen pressure. The crack-growth rate at stress-intensity levels very near the fracture toughness is presumed to be independent of environment. The results are interpreted to suggest that crack growth at high stress intensities is controlled by normal, bulk failure mechanisms such as void coalescence and the like. At intermediate stress-intensity levels the transport of hydrogen to some interaction site along the alpha-beta boundary is the rate-controlling mechanism. The crack-growth behavior at low stress intensities suggests that the hydrogen interacts at this site to produce a strain-induced hydride which, in turn, induces crack growth by restricting plastic flow at the crack tip.
Williams, D. P.↗
Load interaction effects on fatigue crack growth in Ti-6Al-4V alloy
The importance of delay, retardation in the rate of fatigue crack growth, produced by load interactions in variable amplitude loading, on the accurate prediction of fatigue lives of engineering structures is discussed. The effects of a broad range of loading variables on delay in fatigue crack growth at room temperature are examined for a mill annealed Ti-6Al-4V alloy. The results are used to estimate crack growth behavior under programmed loads.
Wei, R. P.↗
Cracking of Ti-6Al-4V in methanol solutions containing sulfates.
Whether cracking of unnotched Ti-6Al-4V specimens occurs in methanol containing H2SO4, Li2SO4, or Fe2(SO4)3 is a function of the age of the solution and the concentration of the sulfate. With H2SO4 concentrations of 0.10 N to 0.25 N, the methanol solutions lose their ability to crack the specimens with time after mixing and prior to exposure. The aging time required to inhibit the cracking varies inversely with the water content of the solution. With larger quantities of H2SO4, 0.5 N and 1 N, no cracking is observed. Interpretations of Raman spectroscopic studies of the aging solution suggests that the nature of the O-H group may play a role in the crack initiation or inhibiting mechanism.
Haney, E. G.↗
2s-2p transitions in the spectra of Ca XVII and Ti XIX.
Identifications of energy level transitions in the Ca XVII and Ti XIX spectra in the regions of 190-360 A and 160-300 A, respectively, are presented for the first time. Lines corresponding to the transition arrays concerned are identified and classified. Extrapolation procedures are described in detail.
Goldsmith, S.↗
The influence of temperature on fatigue-crack growth in a mill-annealed Ti-6Al-4V alloy
To understand the influence of temperature on the rate of fatigue crack growth in high strength metal alloys, constant load amplitude fatigue crack growth experiments were carried out using a 1/4 inch thick (6.35 mm) mill-annealed Ti-6Al-4V alloy plate as a model material. The rates of fatigue crack growth were determined as a function of temperature, ranging from room temperature to about 290 C and as a function of the crack tip, stress intensity factor K, in dehumidified high purity argon environment. The dependence of the rate of fatigue crack growth on K appears to be separable into two regions. The transition correlates with changes in both the microscopic and macroscopic appearances of the fracture surfaces, and suggests a change in the mechanism and the influence of microstructure on fatigue crack growth.
Wei, R. P.↗
Effect of outdoor exposure at ambient and elevated temperatures on fatigue life of Ti-6Al-4V titanium alloy sheet in the annealed and the solution treated and aged condition
Specimens of Ti-6Al-4V titanium alloy sheet in the annealed and the solution-treated and aged heat-treatment condition were exposed outdoors at ambient and 560 K (550 F) temperatures to determine the effect of outdoor exposure on fatigue life. Effects of exposure were determined by comparing fatigue lives of exposed specimens to those of unexpected specimens. Two procedures for fatigue testing the exposed specimens were evaluated: (1) fatigue tests conducted outdoors by applying 1200 load cycles per week until failure occurred and (2) conventional fatigue tests (continuous cycling until failure occurred) conducted indoors after outdoor exposure under static load. The exposure period ranged from 9 to 28 months for the outdoor fatigue-test group and was 24 months for the static-load group. All fatigue tests were constant-amplitude bending of specimens containing a drilled hole (stress concentration factor of 1.6). The results of the tests indicate that the fatigue lives of solution-treated and aged specimens were significantly reduced by the outdoor exposure at 560 K but not by the exposure at ambient temperature. Fatigue lives of the annealed specimens were essentially unaffected by the outdoor exposure at either temperature. The two test procedures - outdoor fatigue test and indoor fatigue test after outdoor exposure - led to the same conclusions about exposure effects.
Phillips, E. P.↗
Relation between surface slip topography and stress corrosion cracking in Ti-8 wt % Al
The deformation behavior of Ti-8 wt % Al has been investigated in an inert environment (air), and an aggressive environment (salt water). Details of surface slip geometry were examined by high resolution surface replicas at various stages of deformation in both environments. Specimens aged to contain a fine dispersion of Ti3Al precipitates failed by subcritical crack growth in salt water, whereas specimens in the single phase condition showed no effects of environment on the yield or fracture characteristics. The Ti3Al precipitates produce little change in strength level or slip character compared to the single phase alloy, and there is no evidence of any effects of environment on the character of surface slip. Rather, the presence of trenches along slip bands on the surface of aged specimens suggest that the specific effect of the Ti3Al precipitates is to render the surface slip steps chemically active relative to the surrounding matrix by slip induced dissolution of the particles.
Boyd, J. D.↗
Combined effects of weld-induced residual stresses and flaws on the fracture strength of Ti-5Al-2.5Sn
The combined effects of weld-induced residual stresses and flaws on fracture strength were experimentally evaluated by testing Ti-5Al-2.5Sn surface flawed specimens at -320F (-195C) in liquid nitrogen. Flaws were located in weld metal with crack planes either parallel to or perpendicular to gas tungsten arc weld centerlines, and in base metal with the crack plane perpendicular to the rolling direction. Tests were conducted using two different flaw sizes to effect fracture stresses at two different levels including one level either at or near, and one level well below the tensile yield strength. Three different residual stress levels were generated, measured, and tested. Results were evaluated using modified linear elastic fracture mechanics theory.
Hall, L. R.↗
Crack growth in Ti-8Al-1Mo-1V with real-time and accelerated flight by flight loading
Crack growth in Ti-8Al-lMo-lV was measured and calculated for real time and accelerated simulations of supersonic airplane loading and heating. Crack-growth rates calculated on the assumption that an entire flight could be represented by a single cycle predicted the experimental rates poorly. Calculated crack growth rates were slower than the experimental rates for all tests with flight-by-flight loading. For room temperature accelerated tests, the calculated rates agreed well with the experimental rates; but the calculations became progressively less accurate for progressively more complex test conditions (tests that included elevated temperature).
Imig, L. A.↗